Yoshifumi Kamikubo RT, Presenter: Nothing to Disclose

Terumitsu Hasebe MD, Abstract Co-Author: Nothing to Disclose

Ryochi Ishibashi MD, Abstract Co-Author: Nothing to Disclose

Yukio Nara RT, Abstract Co-Author: Nothing to Disclose

Mutsumi Higuchi MD, Abstract Co-Author: Nothing to Disclose

Keiko Nakano MD, Abstract Co-Author: Nothing to Disclose

Prostate movements are problematic for radiotherapy with its associated tight margins and dose escalation. The daily prostate position is influenced by the bladder and rectal volumes, and one of the most problems with dose escalation is that of rectal or bladder injury. The purpose of this study is to investigate the overall precision of a new integrated CT-LINIAC system when compared with conventional skin marking system for radiotherapy of prostate cancer.

The CT-LINIAC system consists of a CT scanner and a linear accelerator installed in the same treatment suite and sharing a common table and couch. The patient is scanned by the CT scanner, which is movable on a pair of horizontal rails. The exact location of the organs is identified. These positions are then compared with the planned positions using conventional skin marking system. The daily movement of the prostate was corrected and a new isocenter derived. We treated prostate cancer patients (Stage T1 – T3, N0, M0) using CT/LINAC system with tracking of the daily prostate motion for the consecutive thirteen to fifteen sessions of each patient (84 patients/1231 sessions). Forty one patients (Group A) were pre-treated to drain the rectal air, and 43 patients (Group B) were collected urine in the bladder before the radiotherapy. The patient was treated (72 – 76 Gy) immediately using the new isocenter. Dose-volume histograms were generated for the rectum wall and bladder. Side effects were graded on a 1 – 4 scale, adopted from Radiation Therapy Oncology Group and Late Effects Normal Tissue Task Force criteria.

Of the 108 patients with primary prostate cancer, we studied the motion of the prostate for 20 patients (A: 10 patients; B: 10 patients) during 300 scans by assessing the position of remarkable calcifications in the prostates. In the AP-PA direction 27.9% (A) & 19.36% (B) required a shift of >5 mm and < 10 mm, and 9.7% (A) & 4.64 (B) required a shift of >10 mm. In the superoinferior direction, 13.5% (A) & 14.7% (B) required a shift of >5 mm and < 10 mm, and 0% (A) & 0.64% (B) required a shift of >10 mm. In the right–left direction, 10.73% (A) & 4.16% (B) required a shift of >5 mm and < 10mm, and 0% required a shift of >10 mm. Only 3 patients had side effects (Grade2: 2; Grade3:1).

The CT/LINAC system bears an enormous potential for the correction of interfractional treatment errors, and this technology can be generalized to the treatment of other tumors in the body, especially if the treatment target is subjected to daily interfractional internal organ motion.

Kamikubo, Y, Hasebe, T, Ishibashi, R, Nara, Y, Higuchi, M, Nakano, K, Image-guided Radiotherapy for Prostate Cancer Using a New Integrated CT-LINIAC System.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5006506.html